An absence of matches

On my maternal side of the tree, I was able to use the Leeds Method to break through the long standing brick wall and identify a missing branch of the family. When trying that same method on my Dad's side of the tree, I'm running into an absence of matches. His results only show 13 matches between the range of 400-90 centimorgans on Ancestry, and one other match when I include the matches from MyHeritage.

If I go by the dot method, there is only 456 matches in the O'Brien/Lamon group. When I narrow that group to O'Brien/Bridget matches, I am left with 76, and most of those are connected to the Pittsburgh O'Brien group. I need to try some other approaches if I'm going to identify matches who might point me in the direction of the family of my 3rd-great-grandmother Bridget.